Liquid-liquid contact extractor



June 27, 1961 E. E. WINTER ETI'AL ,2

LIQUID-LIQUID CONTACT EXTRACTOR Filed Jan. 29, 1958 3 Sheets-Sheet 1 ER/c E WINTER STEWART H. RUSSELL BYM Y A TTORNEYS.

June 27, 1961 E. E. WINTER ETAL 2,990,254

LIQUID-LIQUID CONTACT EXTRACTOR 5 Sheets-Sheet 2 Filed Jan. 29, 1958 /NVENTORS ER/c E. WINTER STEWART H. Russnz. BY MY A TTORNEYS.

June 27, 1961 E. E. WINTER ETAL LIQUID-LIQUID CONTACT EXTRACTOR Filed Jan. 29, 1958 3 Sheets-Sheet 3 l/v VE/VTORS R/c E. WINTER STEM/A RT H. Russ/5L L ATTORNEYS. v

Unite tates Patent 2,990,254 LIQUID-LIQUlD CONTACT EXTRACTOR Eric Elliot Winter and Stewart H. Russell, both of Deep River, Ontario, Canada, assignors to Atomic Energy of Canada Limited, Ottawa, Ontario, Canada, a company of Canada.

Filed Jan. 29, 1958, Ser. No. 711,842 11 Claims. (Cl. 23-2705) The present invention relates to a liquid-liquid contact extractor for immiscible liquids and more particularly to an extractor of the multistage mixer-settler continuous countercurrent type. i

Liquid-liquid contact extractors of the continuous countercurrent type are usually constructed in multistage form whereby the heavy liquid phase enters the extractor and proceeds by a plurality of stages through mixers and settlers. The light liquid phase, immiscible with the heavy liquid phase, enters the opposite end of the extractor and proceeds, countercurrent to the heavy liquid phase, through the same series of mixers and settlers. If the heavy liquid phase is the phase being treated, the light liquid phase containing the transferred components and the heavy liquid phase in treated form are drawn oil from the opposite ends of the extractor to which they entered. An example of application of such extractors is in the extraction of uranium and plutonium from one aqueous phase through the use of tributyl phosphate solvent.

Extractors at present in use sulfer from the disadvantage that the mixer-settler units are stacked in series in a vertical column in order to employ gravity to move one of the liquid phases. Units vertically stacked to form a column sulfer from the disadvantage that expensive shielding is necessary when activated liquids such as those containing solutions of irradiated uranium or plutonium are used. In order to avoid the use of vertical shielding it has been suggested to employ mixer-settler units in horizontal arrangement, employing moving parts such as mechanical stirrers to move the liquid phases. However, such extractors are disadvantageous since maintenance is difiicult when activated liquids are used.

The present invention overcomes these disadvantages by providing a plurality of mixer-settler units arranged in horizontal stages, the means for mixing and moving the liquid phases being a flow of gas such as air. As a result, no moving parts are required in the apparatus and the units may be arranged horizontally in multistage series so that the cost of shielding the device is materially reduced and the design is simplified to provide easier accessibility.

The invention, by its broadest aspect, comprises a plurality of mixer-settler units arranged in a series of horizontal stages, an upwardly extending partition separating each of said units into a mixing section and a settling section, a vertical lift tube positioned in each mixing section spaced from the bottom and from the top thereof, a gas inlet opening in the bottom of each mixing section and centered below the lift tube, means leading to each mixing section from the lower zone of the settling section of the next preceding unit to transfer heavy liquid phase from said preceding unit to said mixing section, means leading to each mixing section from the upper zone of the settling section of the next succeeding unit to transfer light liquid phase from said succeeding unit to said mixing section, an inlet for heavy liquid phase and an outlet for light liquid phase positioned in the first of the series of units, an inlet for light liquid phase and an. outlet for heavy liquid phase positioned in the last of the series of units,. and means associated with the gas inlet to deliver gas into each mixing. section.

One embodimentof the invention will. now be described with reference to the accompanying drawings in which:

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FIGURE 1 is a plan view, partly broken away, of a multi-stage extractor according to the invention;

FIGURE 2 is an elevation of the device; and

FIGURE 3 is an end elevation taken along the line 3-3 of FIGURE 1.

The device comprises an elongated box-shaped closed housing 1 divided by walls 2 into separate compartments or units 3 arranged in a series of horizontal stages from one end 4 to the other end 5 of the housing.

Each unit 3 contains a vertical lift tube 6 positioned adjacent one end wall 7 thereof, end wall 7 being a portion of the side of housing 1. The internal passage 6a of tube 6 may be of any suitable internal shape to pro vide turbulence for fluids passing therethrough. The lower end 8 of tube 6 is spaced from the bottom 9 of housing 1 while the upper end 10 of tube 6 is spaced from the top 20 of the housing, preferably terminating in the central zone of the housing.

Tube 6 is mounted in unit 3 preferably by means of a horizontal plate 11 which is fixed to end wall 7 and to each of walls 2 which comprise the sides of the particular unit. Tube 6 may be threaded into plate -11 and provided with a knurled knob 6b for vertical adjustment.

The fourth edge of plate 11 in each unit 3 is supported by a vertical plate or partition 12 which has its lower edge fixed to bottom 9 of housing 1 and its sides fixed to walls 2. The upper edge 13 of vertical plate 12 terminates above horizontal plate 11. Plate 12. thus partitions unit 3 into a mixing section 14 containing tube 6 and a settling section 15. Mixing section 14 is in turn divided by plate 11 into an upper portion 14a and a lower chamber 1412.

Horizontal plate 11 has an opening 16 adjacent end Wall 7 of unit 3 and one wall 2 of the unit to provide communication between upper portion 14a and chamber 14b of mixing section 14 external of tube 6. Bottom 9 of housing 1 carries an inlet opening 17 centered beneath each tube 6.

The position of the mixing section 14 and settling section 15 is reversed in each succeeding unit of the extractor so that mixing section 14 in one unit is adjacent settling'section 15 in the preceding and succeeding units of the device.

A- conduit 18 external of housing 1 connects the lower zone of settling section 15 of each unit 3 with the upper portion 14a of mixing section 14 of the next succeeding unit. Conduit 18 opens from the lower zone of settling section 15 adjacent bottom 9 thereof and opens into upper portion 14c adjacent opening 16 of horizontal plate 11.

A conduit 19 external of housing 1 connects the upper zone of settling section 15 of each unit 3 with chamber 14]) of the mixing section 14 of the next preceding unit. Conduit 19 opens from unit 3 above the upper end 10 of tube 6 and below the top 20' of housing 1. The opening of conduit 19 into chamber 14b is positioned at a suitable point below plate 11.

In end wall '4 of housing 1 an opening 21 is provided leading into chamber 14b of mixing section 14 of the first unit 3 in the series. An opening 22 is also provided in end wall 4 leading from the upper part of settling section 15 of the first unit 3 of the series. Similarly, in end wall 5 an opening 23 is provided leading from the lower zone of settling section 15 of the last unit in the series and an opening 24 is provided into chamber 14b of mixing section 14 of the last unit 3 of the series. In addition, a series of probe openings 25 are provided in end wall 5 at various levels above bottom 9'. Probe openings 26 are also provided in top 20 of housing 1 for each unit 3, above settling sections 15.

Conduits 27 lead from a common source to each inlet opening 17 in bottom 9 of housing 1'.

Walls 2 separating units 3 terminate below top 20 0f housing 1 to provide a vent 28 for each unit. A central flanged vent 29 is positioned centrally in top 20 to carry the spent fluid away. If the vented fluid contains active spray, suitable means maybe provided for purification.

In the operation of the device a heavy liquid phase to be purified or otherwise treated enters housing 1 through opening 21 in end wall 4 into chamber 141; of mixing section 14 of the first of the series of mixer-settler units 3. A gas, preferably air, enters chamber 14b through conduit 27 and draws the heavy liquid phase up through lift tube '6 into the upper portion 14a of the mixing section. The heavy liquid phase then passes into settling section 15 where it drops to the lower zone thereof because of its higher density. From the lower zone of settling section 15 the heavy liquid phase is drawn through conduit 18 into the upper portion 14a of mixing section 14 of the next succeeding unit 3 where it flows through opening 16 of plate 11 back into chamber 14b and is again drawn up through lift tube 6 of that mixing section and passes into the settling section 15 of that unit. The drawing action in chamber 14b creates suction at opening 16 which draws the heavy liquid phase through conduit '18. The heavy liquid phase is drawn into upper portion 14a rather than directly into mixing chamber 14b in order that plate 11 may act as a weir and prevent excess pump action by the suction created in chamber 1417 which would lower the interface in the preceding settling section from which the heavy liquid phase is drawn.

The light liquid phase or solvent enters housing 1 through opening 24 in end wall into the chamber 14b of mixing section 14 of the final mixer-settler unit 3 of the series. From chamber 14b the light liquid phase is drawn up through tube 6 and enters settling section 15 of each unit 3 Where it remains in the upper zone of that section due to its lighter density. Conduit 19, acting as a weir, to prevent excess draw oif conducts the light liquid phase from settling section 15 down into chamber 14b of mixing section 14 of the next preceding unit 3 in the series. The light liquid phase is drawn through conduit 19 by the suction created in chamber 14b. In chamber 14b of this next proceeding unit the light liquid phase is again drawn up through lift tube 6 by the action of the fluid entering through inlet opening 16 and, by this action, is intimately mixed with the heavy liquid phase being simultaneously drawn up through tube 6. Emerging from tube 6 the light liquid phase enters settling section 15 and is again drawn 0135 through conduit 19 to the mixing section of the next preceding unit in the series.

By this action, the light and heavy liquid phases are intimately mixed. The heavy liquid phase, depleted in transferable components, is always brought into contact with light liquid phase which is capable of further reducing the content of transferable components. Finally, the depleted heavy phase is drawn off from settling section 15 of the final unit 3 in the series through the opening 23 while the solvent, containing the transferable components, is drawn ofl from the settling section 15 of the first unit 3 of the series through opening 22.

It will be appreciated that some of the heavy liquid phase emerging from lift tube 6 will re-enter that part of mixing section 14 surrounding the tube. Indeed, a substantial portion of both the heavy and light liquid phases will recirculate through opening 16 in horizontal plate 11 back into the lower chamber 14b, where they will again pass up through lift tube 6, if the :feed rate of the gas entering chamber 14b through conduit 27 is appreciable. This recirculation is advantageous since it permits more intimate mixing of the light and heavy phases, thus increasing the efficiency of the unit. If greater recirculation is desired, horizontal plate 11 could be replaced by radial bars holding lift tube '6 in its central position.

Vertical plate 12 prevents the heavy liquid phase, which has passed into section 15 and settled therein, from re- 4 l entering mixing section 14 as long as the interface between the light and heavy liquid phases does not rise above the upper edge 13 of vertical plate 12.

In a modification of the device partition 12 may extend to a point adjacent the top 20 of housing 1, dividing unit 3 into a mixing chamber and a settling chamber. A horizontal slot would then be provided in partition 12 to allow some of the mixed light and heavy phase liquids emerging from tube 6 to enter the settling chamber. This modification would allow greater recirculation of the mixed liquids within each unit 3 of the series.

If desired, a conduit 30 may be provided which leads into each conduit 18 to allow for the addition of fresh heavy or light liquid phases to mixing section 14 of any unit 3 of the series. Samples can be taken from settling sections 15 through probe openings 26 for chemical analysis of the separation process and the addition of fresh liquids governed thereby. In this way still higher efficiency of the extractor can be obtained. Conduit 30 would also allow for the addition of a third liquid to the process, if desired. For instance the light and heavy phase liquids introduced at the ends of the extractor could be clean solvent and nitric acid respectively with a solution of uranium, plutonium and fission products in'nitric acid being introduced intermediate the ends of the extractor.

A process requiring two or more steps could be carried out by means of the present invention. By placing a plurality of extractors in series, liquids flowing from the outlets of a one extractor could be introduced into the next extractor either at the ends or intermediate thereof, thus enabling a complex flow pattern to be obtained.

Of course, the apparatus described could be modified by interconnecting a series of individual units rather than by providing a housing subdivided into such units. Also, the flow of gas through the mixing sections 14 of the apparatus could be eflected either by supplying the gas under pressure or by providing a vacuum in association with vent 29.

It should be noted that the spray from liquids above tube 6 in mixing section 14 will be de-activated to some extent since the gas from the tube passes through the head of liquid between the upper part 10 of tube 6 and the outlet of conduit 19.

What we claim asour invention is:

1. A continuous countercurrent liquid-liquid contact extractor comprising a plurality of mixer-settler units arranged in a series of horizontal stages, an upwardly extending partition separating each of said units into a mixing section and a settling section, a vertical lift-tube positioned in each mixing section spaced from the bottom and from the top thereof, a fluid inlet opening into the bottom of each mixing section and centered below the lift tube, means leading to each mixing section from the lower zone of the settling section of the next preceding unit to transfer heavy liquid phase from said preceding unit to said mixing section, means leading to each mixing section from the upper zone of the settling section of the next succeeding unit to transfer light liquid phase from said succeeding unit to said mixing section, an inlet for heavy liquid phase and an outlet for light liquid phase positioned in the first of the series of units, an inlet for light liquid phase and an outlet for heavy liquid phase positioned in the last of the series of units, and means associated with each fluid inlet to deliver gas into each mixing section.

2. An extractor as claimed in claim 1, wherein each mixing section is divided into an upper portion and a lower chamber by means of a horizontal plate, the lift tube passing through the plate, and an opening positioned in the plate to interconnect the upper portion of the mixing section with the lower chamber.

3. An extractor as claimed in claim 2 wherein the Hit tube is secured to the horizontal plate and vertically adjustable thereon.

4. An extractor as claimed in claim 2 wherein the means leading to each mixing section from the lower portion of the settling section of the next preceding unit opens into the upper portion of said mixing section adjacent the opening in the plate, and the means leading to each mixing section from the upper portion of the settling section of the succeeding unit opens into the lower chamber.

5. An extractor as claimed in claim 1 wherein the means connecting each mixing section with the lower portion of the settling section of the next preceding unit and with the upper portion of the settling section of the next succeeding unit'comprise conduits positioned external of the mixer-settler units.

6. An extractor as claimed in claim 1 wherein the means associated with the fluid inlet openings comprise conduits leading from a common source.

7. An extractor as claimed in claim 1 including means to control the outflow of heavy liquid phase in the last of the series of units thereby to control the interface between the phases in said last unit.

8. An extractor as claimed in claim 1 including means to introduce liquid into the mixing section of at least one mixer-settler unit intermediate the first and final unit of the series.

9. An extractor as claimed in claim 1 wherein the partition extends to the top of the unit, a slot being provided in the partition adapted to allow flow of liquid from the mixing section to the settling section.

10. An extractor of the continuous countercurrent liquidliquid contact type comprising a housing, walls dividing the housing into a series of uni-ts arranged in horizontal stages, a partition extending upwardly into each unit to provide a mixing section and a settling section therein, a vertical lift tube positioned in the mixing section, said tube being spaced from the bottom of the mixing section and having its upper end spaced from the top of said section, an inlet opening into the bottom of the mixing section and centered below the lift tube, a conduit interconnecting each mixing section and the lower zone of the settling section of the next preceding unit, a conduit interconnecting each mixing section and the upper zone of the settling section of the next succeeding unit, and inlet and an outlet positioned in the first of the series of units, an inlet and an outlet positioned in the last of the series of units, means associated with the inlet openings in the bottom of each mixing section to deliver gas thereto, and means to vent gas from the upper portion of each unit.

11. An extractor as claimed in claim 1 wherein each unit comprises a closed housing having at least one vent opening from the upper portion thereof.

References Cited in the file of this patent UNITED STATES PATENTS 1,156,372 Robinson Oct. 12, 1915 1,297,171 Holley et a1. Mar. 11, 1919 1,386,809 Taylor Aug. 9, 1921 2,266,521 Van Dijck Dec. 16, 1941 2,646,346 Coplan et a1 July 21, 1953 2,743,154 Kaufman Apr. 24, 1956 2,851,396 Myers Sept. 9, 1958 OTHER REFERENCES Davis et al.: Chem. Eng. Progress, April 1954, vol. 50, No. 4, pp. 188-197.

Colvin: DP-239, October 1957. 

1. A CONTINUOUS COUNTERCURRENT LIQUID-LIQUID CONTACT EXTRACTOR COMPRISING A PLURALITY OF MIXER-SETTLER UNITS ARRANGED IN A SERIES OF HORIZONTAL STAGES, AND UPWARDLY EXTENDING PARTITION SEPARATING EACH OF SAID UNITS INTO A MIXING SECTION AND A SETTLING SECTION, A VERTICAL LIFT-TUBE POSITIONED IN EACH MIXING SECTION SPACED FROM THE BOTTOM AND FROM THE TOP THEREOF, A FLUID INLET OPENING INTO THE BOTTOM OF EACH MIXING SECTION AND CENTERED BELOW THE LIFT TUBE, MEANS LEADING TO EACH MIXING SECTION FROM THE LOWER ZONE OF THE SETTLING SECTION OF THE NEXT PRECEDING UNIT TO TRANSFER HEAVY LIQUID PHASE FROM SAID PRECEDING UNIT TO SAID MIXING SECTION, MEANS LEADING TO EACH MIXING SECTION FROM THE UPPER ZONE OF THE SETTLING SECTION OF THE NEXT SUCCEEDING UNIT TO TRANSFER LIGHT LIQUID PHASE FROM SAID SUCCEEDING UNIT TO SAID MIXING SECTION, AN INLET FOR HEAVY LIQUID PHASE AND AN OUTLET FOR LIGHT LIQUID PHASE POSITIONED IN THE FIRST OF THE SERIES OF UNITS, AN INLET FOR LIGHT LIQUID PHASE AND AN OUTLET FOR HEAVY LIQUID PHASE POSITIONED IN THE LAST OF THE SERIES OF UNITS, AND MEANS ASSOCIATED WITH EACH FLUID INLET TO DELIVER GAS INTO EACH MIXING SECTION. 